Nutrient uptake by embryos of the Australian viviparous lizard Eulamprus tympanum

Eulamprus tympanum is a high-altitude viviparous lizard that was probably u sed to help define a Type I chorioallantoic placenta. In this article, we ( 1) describe the net transport of nutrients across the placenta of E. tympan um, and (2) compare placental uptake in E. tympanum with a previous study o f Eulamprus quoyii, which occurs in warmer environments, to assess the pote ntial importance of thermal regime on placentotrophy. Freshly ovulated eggs are mg. There is a significant 387.3 +/- 19.7 net uptake of water and a ne t loss of dry matter during development, so the dry neonate is only 84% the size of the dry egg. There is no significant change in the total ash or ni trogen in eggs during embryonic development, with the entire loss of dry ma tter being lipid. Almost the entire loss of lipid occurs in the triacylglyc erol fraction, with no net change in phospholipids. A net increase in total cholesterol suggests that cholesterol is synthesised by the developing emb ryo. The lipid profile of eggs of E. tympanum reflects that of other specie s with simple placentae in having a relatively high proportion of triacylgl ycerol and little cholesterol. The fatty acid composition of eggs reflects that expected in the diet of E. tympanum. There is a preservation and some synthesis of arachidonic (20:4n-6) and docosahexaenoic (22:6n-3) acids in t he phospholipid fraction during embryonic development. Despite there being no net uptake of ash, there is a net increase in calcium, potassium, sodium , and magnesium in the neonate compared with the egg. We conclude that E. t ympanum, like E. quoyii, is predominantly lecithotrophic with little, if an y, uptake of organic molecules but with significant uptake of some inorgani c ions and water. In addition, there is no difference in placentotrophy cor related with differences in the environments inhabited by each species.